Devices for driving fasteners fed from a magazine one at a time in front of a mechanical, electrical, hydraulic or pneumatic driving means have long been known. It is also known in the prior art to feed the fasteners in front of the driving means from a magazine by connecting the fasteners to each other in a strip which is mounted in the magazine. However, the indexing of the strip and the separation of the fasteners from the strip for driving have presented problems and a number of different solutions have been proposed, none of which have been entirely satisfactory.
For example, it has been proposed to provide a separate shifting mechanism or device which removes the fasteners from the strip at a point spaced from the driving channel and carries them into the driving channel. U.S. Pat. No. 354,462, issued Dec. 14, 1886 to C. W. Copeland; U.S. Pat. No. 2,982,595, issued May 1, 1961 to C. E. Rogers, Jr.; and U.S. Pat. No. 3,623,646, issued Nov. 30, 1971 to Adolph Cast are representative of this solution to the problem. However, it will be understood that the shifting mechanism must be operated by the means for driving the fasteners thus extracting power from the driving action and adding an additional mechanism subject to jamming in operation.
It has also been proposed in the prior art to connect the fasteners to each other by means of a friable strip or tape which is shorn or fragmented by the driving means during the driving stroke to separate the driven fastener therefrom. U.S. Pat. No. 3,554,246 issued Jan. 12, 1971 to Donald B. Halsted, is representative of this solution to the problem. However, the fragments of the strip or tape tend to interfere with the driving operation since they are either thrown onto the surface of the workpiece where they may pass underneath the fastener being driven, or they are retained in the driving mechanism where they may cause jamming.
Finally, it has been proposed in the prior art to connect the fasteners to each other by means of a strip or tape having fastener gripping portions designed to flex when contacted by the driving means during the driving operation to cause the release of a fastener for driving. U.S. Pat. No. 3,543,987, issued Dec. 1, 1970 to Allen R. Obergfell et al.; U.S. Pat. No. 3,550,831, issued Dec. 29, 1970 to Allen R. Obergfell et al.; and U.S. Pat. No. 3,971,421, issued July 27, 1976 to H. E. Damratowski are representative of this solution to the problem. However, the basically contradictory requirements that the tape and mechanism provide a secure connection of the fasteners to the tape for storage and positioning and yet allow the driven fastener to be separated from the tape by the driving means without damage to the tape or jamming of the mechanism makes this solution to the problem difficult and of marginal effectiveness.
The present invention is directed to overcoming one or more of the problems as set forth above.